okay first thank you :DD but what you do is that you go to the drawing thingy than go to the frame selector, than click background and it’ll give you a thing saying if you want to pay for a membership or watch an ad, click watch an ad, watch the ad than there you get the background for free :D
now to do what i did all you have to do is go to the background and scribble a bunch of colors that go to the actual top layer and use the paint hi hey to just make it black, than just erase where you want to draw and it comes out like that :DD
(ik i explained it bad so i can send a screen recording of how i did it of you want lol)